A support arm having a gravity compensation function to keep balance with gravity acting on the arm has conventionally been known. In connection with such an apparatus, for example, Japanese Patent Laying-Open No. 2003-181789 (PTL 1) discloses a mechanical gravity compensation apparatus aiming to keep balance of an actuation arm with gravity with a simplified structure with respect to three axes orthogonal to one another in a space.
In addition, Japanese Patent Laying-Open No. 2004-299024 (PTL 2) discloses a cable guide in a joint portion of a robot or the like aiming to realize a shorter dimension of a cable without increase in size of the joint portion. Moreover, Japanese Patent Laying-Open No. 2003-89090 (PTL 3) discloses a multi joint arm mechanism aiming to mitigate drive load of an arm, by counteracting against a weight of each arm having multiple joints with constant tensile force.